1. Field of the Invention
The invention relates to a computer system and a restoration method and is suited for use in, for example, a computer system equipped with a storage apparatus having a backup function and a restoration function.
2. Description of Related Art
Currently, data backups using a remote copy technique are widely employed particularly in large companies' and the government's computer systems in order to protect data from data destruction caused by large-scale natural disasters such as earthquakes or hurricanes, human-caused disasters such as system administrators' operation mistakes or terrorism attacks, and equipment and program failures.
By setting a logical volume (hereinafter referred to as the “primary volume) in a primary-side storage apparatus (hereinafter referred to as the “primary storage apparatus”) and a copy destination logical volume (hereinafter referred to as the “secondary volume”) in a secondary-side storage apparatus (hereinafter referred to as the “secondary storage apparatus”) to form a copy pair in this type of computer system, data written to the primary volume is transferred to the secondary storage apparatus in synchronization with or out of synchronization with writing of the data to the primary volume. Then, at the secondary storage apparatus, the data transferred from the primary storage apparatus is written to the same position in the secondary volume as that in the primary volume.
If data in the primary volume of such a computer system is lost or destroyed due to natural disasters or human-caused disasters, it is possible to restore the primary volume to the state before the data loss or destruction by copying data of necessary files in snapshots stored in the secondary volume to the primary volume.
If this type of computer system is used, it is possible to duplicate data and retain dual pieces of data, and prevent data loss due to, for example, disasters.
As conventional restoration methods for such a computer system, there are a volume-based copying method for copying data of files to be restored from the secondary volume to the primary volume on a volume basis and a file-based copying method for copying snapshot data from the secondary volume to the primary volume on a file basis.
The volume-based copying method is a method of differential copying of data in all the files in the secondary volume from the secondary volume to the primary volume on a volume basis. Since the entire content of the primary volume is overwritten by this restoration method, this method cannot be used when there are files not to be restored. However, since data is directly transferred from the secondary storage apparatus to the primary storage apparatus by this method, a data transfer speed is fast.
The file-based copying method is a method of differential copying of data from the secondary volume to the primary volume on a file basis. This restoration method is effective when there are files not to be restored. However, since individual files are transferred via an external server from the secondary storage apparatus to the primary storage apparatus by this method, a data transfer speed is slow.
Both the volume-based copying method and the file-based copying method have advantages and disadvantages, respectively. So, when restoring data, users need to judge which restoration method should be used, depending on an object to be restored. Therefore, the problem is that making such a judgment requires time and effort; and if the user mistakenly makes a bad judgment, restoration work will require extra time.
Incidentally, Japanese Patent Application Laid-Open (Kokai) Publication No. 2005-301497 discloses a restoration method technique capable of restoring data at a high speed. However, there is a demand for a restoration technique that can utilize more functions of existing computer systems and can be implemented by a slight change of programs.